BATTERY OR ALTERNATOR QUESTION
 

My wife just called me, she was driving the car and got a battery light on, few miles later all the lights came on, the message display shutoff and she pulled over, seems like the car died. She has mentioned a Transm Failure Light...Is it a Battery or Alternator considering the car died like this during driving? Thank You for your help,

B

Alternator...probably...The car won't usually just shut off while your driving if its just the battery. But I'm not 100 percent sure..

My money is on the alternator. My 330 did the same thing.....battery light came on, then the radio started cutting in and out. Made it home, hooked up a meter to the car (read 8.8VDC), turned the car off, and never came back on until I replaced the alternator.

What size engine do you have?

it is 2002 x5 4.4i

also..I am not sure if it makes a difference...battery has never been replaced at 110k miles and 6 years

If you are able to start the car (or jump start it) and if you have a digital mutlimeter, measure the voltage to the X5. If it's below 12 VDC, then the alternator (or voltage regulator) is toast.

I think the V8 alternator is liquid cooled.

Dan

What voltage should it read while car is idling?

13.8 to 14.8v at the battery if the alternator is charging properly. Sounds like the alternator died and it ran off the battery until it died.

Yup, dropped my altternator off yesterday to get rebuilt. Mine was reading 11.8 while idle and 12.1 with car off.

Good luck with the rebuild. Keep us informed.

Daniel